Improved angina threshold and coronary reserve following direct myocardial revascularization

Angina threshold, coronary reserve, and global myocardial lactate metabolism were studied by atrial pacing in 18 patients with obstructive coronary artery disease before and after aortocoronary artery bypass (ACB) surgery. In 3 of these 18 patients, regional (anterior wall) metabolism was also studied. Following ACB, 16 of the 18 patients did not develop angina at the maximum pacing rate (MPR). One patient developed angina postoperatively at a similar rate as before surgery. In the other patient, postoperative angina threshold was much higher. In the group as a whole, postoperative MPR (159 +/- 3.5 beats/min) was much higher than the preoperative angina rate (124.9 +/- 4.9 beats/min; P less than 0.001). Rate-pressure product (RP) at MPR postoperatively (21.5 +/- 0.89 mm Hg/min X 10(-3)) was also higher than RP at angina rate preoperatively (18.8 +/- 0.92 mm Hg/min X 10(-3); P less than 0.01). Although coronary sinus blood flow (CSBF) both at rest (152 +/- 16.2 ml/min) and at MRP (266 +/- 27.5 ml/min) postoperatively was higher than preoperative CSBF at rest (111 +/- 10.7 ml/min; P less than 0.05) and at angina rate (202 +/- 19.9 ml/min; P less than 0.05), arterial-coronary sinus O2 content (Art.-CSO2) difference was significantly lower postoperatively both at rest (8.9 +/- 0.37 ml/min) and at MPR (9.1 +/- 0.44 ml/min) compared with the preoperative Art.-CSO2 at the rest (12.7 +/- 0.40 ml/min; P less than 0.01) and at angina rate (12.4 +/- 3.8 ml/min; P less than 0.01)...